Formal (3+3) Cycloaddition of Silyl Enol Ethers Catalyzed by Trifric Imide: Domino Michael Addition–Claisen Condensation Accompanied with Isomerization of Silyl Enol Ethers

We describe here a Tf2NH-catalyzed formal (3+3) cycloaddition of silyl enol ethers with acrylates as a new domino reaction. In the domino sequence, the catalyst activates Michael addition, deprotonation of the resulting silyloxonium cation and intramolecular Claisen condensation. It was found that reaction modes significantly depend on the reaction temperature. We also examined the mechanistic detail of the reaction by 1H-NMR experiment.